Tropical Storm DOLPHIN Advisory Fri May 08

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 07W (SEVEN) WARNING NR
08//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 07W (SEVEN), LOCATED APPROXIMATELY 95 NM
SOUTH-SOUTHWEST OF KOSRAE, HAS TRACKED EASTWARD AT 04 KNOTS OVER THE
PAST SIX HOURS. THE SYSTEM IS BEING STEERED IN AN ATYPICAL EASTWARD
DIRECTION BY ENHANCED LOW- TO MID-LEVEL, NEAR-EQUATORIAL WESTERLY
FLOW. THE CURRENT POSITION IS BASED ON A 071132Z PGTW SATELLITE FIX
AND A 081016Z ASCAT PASS. THE INTENSITY OF 35 KNOTS IS CONSISTENT
WITH DVORAK SATELLITE INTENSITY ESTIMATES FROM PGTW AND KNES. TS 07W
LIES EQUATORWARD OF AN UPPER-LEVEL RIDGE AXIS, IN AN AREA OF
MODERATE SOUTHEASTERLY VERTICAL WIND SHEAR AND STRONG WESTWARD AND
POLEWARD DIFFLUENCE ALOFT. DEEP CONVECTION HAS DEVELOPED OVER THE
CIRCULATION CENTER, ALTHOUGH THE MAJORITY OF THE CONVECTION
ASSOCIATED WITH THE SYSTEM REMAINS CONFINED TO THE NORTHWESTERN
PORTION OF THE LOW-LEVEL CIRCULATION CENTER DUE TO THE PERSISTENT
SHEAR.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS 07W IS EXPECTED TO TURN POLEWARD AND EVENTUALLY WEST-
NORTHWESTWARD OVER THE NEXT 72 HOURS AS A BUILDING SUBTROPICAL RIDGE
TO THE NORTH BECOMES THE PRIMARY STEERING MECHANISM. DECREASING
VERTICAL WIND SHEAR, INCREASING WESTWARD AND POLEWARD OUTFLOW, AND
PASSAGE OVER VERY WARM WATER WILL ALLOW THE SYSTEM TO CONTINUE
INTENSIFYING. NUMERIC MODELS ARE IN POOR AGREEMENT REGARDING THE
ORIENTATION OF THE UPCOMING TURN TO THE NORTHWEST AND ASSOCIATED
TRACK SPEEDS. THE FIRST 72 HOURS OF THE CURRENT TRACK FORECAST IS
CONSISTENT WITH A GROUPING OF MODELS THAT INCLUDES A MAJORITY OF
CONSENSUS MEMBERS. BECAUSE OF THE COMPLEX STEERING PATTERN AND NOTED
MODEL SPREAD, TRACK FORECAST CONFIDENCE IS LOW.
   C. IN THE EXTENDED RANGE, TS 07W WILL CONTINUE TRACKING GENERALLY
WEST-NORTHWESTWARD UNDER THE STEERING INFLUENCE OF THE SUBTROPICAL
RIDGE. FAVORABLE UPPER-LEVEL SUPPORT AND PASSAGE OVER WARM WATER
WILL SUPPORT ADDITIONAL INTENSIFICATION. NUMERICAL MODEL SPREAD, IN
TERMS OF TRACK DIRECTION AND SPEED, REMAINS SIGNIFICANT IN THE
EXTENDED PERIOD WITH NO APPARENT PRIMARY GROUPING. THE CURRENT
EXTENDED RANGE FORECAST LIES NEAR THE MULTI-MODEL CONSENSUS, WITH
LOW CONFIDENCE.//
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